Time-dependent effects of vagotomy on pancreatic polypeptide release

It has been suggested that the pancreatic polypeptide response to a meal is inhibited by truncal vagotomy but returns towards normal with time. We have examined this hypothesis by measuring the pancreatic polypeptide response to a meal in five dogs before and 1 and 6 months after truncal vagotomy. Pancreatic polypeptide responses to food were significantly inhibited (P less than 0.01) in both postoperative studies. However, comparison of the 1- and 6-month responses revealed a significant increase (P less than 0.05) in the magnitude of the second hour response from 2.3 +/- 1.5% of the preoperative response at 1 month to 21.3 +/- 9.6% at 6 months. The pancreatic content of pancreatic polypeptide in four vagotomized dogs (1.06 +/- 0.06 nmol/g) was not significantly different from normal (1.30 +/- 0.33 nmol/g). These studies have shown that truncal vagotomy permanently inhibits the early phase of pancreatic polypeptide release but that the magnitude of the late phase response increases with time. Whether the response would ever return to that observed before vagotomy is uncertain.